In the dental imaging field, a cephalometric imaging device includes an x-ray source that emits a conical or pyramidal shaped x-ray beam towards a cephalometric imaging sensor mounted at the end of a long arm. A patient's positioning unit to position the patient's head is located between the x-ray source and the cephalometric sensor at the vicinity of the cephalometric sensor. Then, the x-ray beam originating from the remote x-ray source radiates the patient's skull before impinging the cephalometric sensor. The digitalization of the signal and the treatment of the data lead to the reconstruction of a projection image of the skull or at least a part of the skull of the patient.
In a general dental cephalometric imaging device, a distance between the x-ray source and the cephalometric sensor is typically 1.7 m. As the patient's positioning unit located at the vicinity of the cephalometric sensor and away from the x-ray source, the magnitude ratio of the image size to the patient's skull size is close to 1 for any part of the skull. In particular in profile imaging, a first half of the skull is closer to the sensor than the other half. Thanks to the small ratio of the source-sensor distance to the source-patient distance, the magnitude factor for the projection of both halves of the skull on the cephalometric sensor along the conical x-ray beam is almost the same and distortion of the image is then reduced or avoided.
The cephalometric sensor can have the shape of a thin vertical cylinder with a large (e.g., typically 30) height-to-width ratio. A collimator having the same shape as the cephalometric sensor is used to collimate the x-ray beam originating from the remote x-ray source. This collimator is positioned in front of the patient's positioning unit and in coincidence with the cephalometric sensor so that the x-ray beam is shaped before radiating the patient. The cephalometric imaging process includes accumulating frames of data from the cephalometric sensor while the cephalometric sensor is translated from one side of the skull to the other side (e.g., horizontally, vertically) with a combined and coordinated movement of the collimator. The frames of data are then merged and treated to reconstruct a projection image of the whole skull. In the cephalometric or skull imaging technique, the patient can be positioned facing the x-ray beam or in a profile position.
The collimator according to the prior art is usually made of a plurality of metallic plates assembled in a complicated way, the ensemble being covered by a plastic cover. This makes the prior art collimator complicated and expensive to manufacture. Further, the link between the metallic parts and the plastic cover has to be precisely engineered to avoid any break between each part.
There is still a need for a cephalometric collimator that is easy and/or cheap to manufacture.